The sentence is:

I talk sexual to my boyfriend.


It just doesn't seem right. Is it right?

Nope, doesn't sound right at all. How about... I have sexual conversations with my boyfriend.

Well the person wants to say:

I speak sexually with my boyfriend.. like she is perverted with her boyfriend.

I know it's wrong but I can't seem to find a way to reword it...

You are right, sexual is an adjective when it should be an adverb describing the way she talks.

It helps if you throw an indirect object in the sentence: "I talk to my boyfriend with sexual overtones".